1. Field of the Invention
This invention relates generally to an apparatus and method for sampling tissue. More specifically, the present invention relates to a biopsy device which can be adjusted to allow precise amounts of sample tissue to be collected thereby.
2. Prior Art
The removal of minute tissue samples from humans and animals by introducing a needle into the body and catching the sample within the needle, is a frequently used medical practice today. Such samples are necessary for microscopic examination, organ cultures, etc.
The method most commonly followed for obtaining tissue samples has been to use a needle which is formed of an inner solid rod which has a sampling notch in the distal end thereof, in conjunction with a hollow outer cannula which slides thereover and cuts tissue which has been located in the sampling notch of the inner rod. The inner rod, except for its pointed distal end, is located within the cannula when the device is inserted into the tissue to be sampled. The outer cannula is then held stationary while the inner rod is inserted deeper into the tissue. While in this position, tissue moves into the sampling notch of the inner rod just adjacent the pointed distal tip thereof. The inner rod is then held stationary while the outer cannula is slid thereover. Motion of the outer cannula passing over the sampling notch causes the tissue located therein to be severed from surrounding tissue and thereafter to be trapped in the sampling notch as the cannula completely covers the inner needle distal end. Both the outer cannula and the inner rod with the tissue sample secured therein are then simultaneously removed from the patent. The outer cannula is then slid back away from the distal end of the inner rod to allow removal of the tissue sample from the sampling notch thereof. The tissue sample is then examined.
This general method of tissue sampling has been used for several decades and is exemplified in U.S. Pat. No. 3,477,423. As disclosed therein, the needle movements are made manually. This has certain disadvantages, in that movements may not be made fast enough to insure clean and complete severance of a tissue sample. Further, manual operation of the needle generally involves inaccurate movements, and slight lack of coordination between the needle and the cannula. This often causes unnecessary tissue damage and, in the case of infectious or tumorous tissue, can cause spreading of the diseased tissue throughout a larger tissue area. Also, during manual operation of a needle, the patient may move slightly during the introduction thereof into the tissue and cause the needle to its target area. Also, respiratory movements are common for some organs, for example the liver and the kidney, which further may reduce the accuracy of the sampling technique.
An improvement in the above mentioned method of biopsy sampling has been to restrict needle movements by containing the inner rod and outer cannula inside a holder. The holder restricts needle movement to specific directions and also may carry springs therein which drive the rod and cannula through their sampling motions in a rapid and predictable manner. This technique is exemplified in U.S. Pat. No. 4,699,154. Even though this is an improvement over manually actuated needles, it nevertheless carries several disadvantages. For example, the length of the needle movement cannot be adjusted according to the size of the sample desired to be taken. Therefore, unnecessary quantities of tissue may be removed from the tissue sample area causing unnecessary tissue damage and possibly unnecessary spreading of diseased tissue. Further, the forceful introduction of a needle into the tissue area generally causes a certain amount of damage to the tissue in the immediate surroundings of the target area. This is due to the high pressure released from the needle in the injection process.
Therefore, there has long existed a problem in the prior art of controlling the size of a tissue sample taken by the biopsy needle. The size of the sample should not exceed the necessary amount of tissue needed for diagnostic purposes. Since prior art devices have included no ability to adjust the size of sample taken in an accurate manner, they have failed to resolve this problem. Also, a smaller tissue target area, such as a lesion or tumor or the like should be sampled with a shorter movement of the needle and a smaller and more controlled sample size taken thereby. This is because the needle should not pass outside the target area into unaffected area of the tissue, nor should it reach outside of the organ, tumor, lesion, etc. which is being sampled to thereby cause risk of damage to other structures such as adjacent large blood vessels or the like. It is therefore needful to develop an apparatus where the needle movements can be precisely made to allow the physician to collect precisely the desired tissue sample volume predetermined with various imaging methods (e.g. radiological, ultrasound or computer tomography examination) without unnecessary damage to the tissue or surrounding structures.